Recurrence-free survival is prolonged in high-grade serous ovarian cancer with high PD-L1 expression

High-grade serous ovarian carcinoma (HGSOC) is the most common and clinically aggressive epithelial ovarian cancer subtype and is frequently characterized by relapse despite standard treatment. The FIGO staging system guides treatment decisions and provides prognostic information, but patients within the same stage may display markedly different treatment responses and survival outcomes. Increasing evidence indicates that the tumor microenvironment contributes to recurrence and therapeutic responsiveness. This study focused on the PD-1/PD-L1 immune-checkpoint pathway and evaluated PD-1/PD-L1-positive immune-cell density as a potential prognostic biomarker in HGSOC.

This retrospective study included 47 patients with HGSOC and matched recurrent tumor samples. Immunohistochemistry was performed on tissue microarrays constructed from paired primary and recurrent formalin-fixed paraffin-embedded samples. PD-1 and PD-L1 immune-cell densities were quantified on evaluable TMA cores, dichotomized into low- and high-density groups, and correlated with recurrence-free survival (RFS), overall survival (OS), chemosensitivity, and clinicopathological parameters. Kaplan-Meier and Cox regression analyses were used to evaluate survival associations.

Patients with high primary PD-L1 immune-cell density had longer RFS than those with low PD-L1 density (log-rank p = 0.032). In contrast, no significant difference in RFS was observed between patients with high versus low PD-1 immune-cell density (p = 0.18). Neither PD-L1 nor PD-1 density showed a statistically significant association with OS in this cohort.

In this retrospective TMA-based HGSOC cohort, high PD-L1 immune-cell density in the primary tumor was associated with prolonged RFS. These findings should be considered hypothesis-generating and warrant validation in larger, prospectively collected HGSOC cohorts before clinical use.